Such devices are for example used for drawing blood from a bottle or bag or to take a specimen from a collection vessel of for example urine. In every case there is the problem that the elastomeric needle-shield tube that surrounds the needle and that is collapsed like a bellows when the guide sleeve is fitted to or installed on the tip exerts a substantial spring return force acting against the forces that retain the guide sleeve on the tip, with the result that the guide sleeve is pushed off the tip. In order to get around this problem, various measures are taken.
In the blood-drawing device described in German 3,049,503 (US equivalent U.S. Pat. No. 4,449,539), the cap closing the outer end of the specimen tube has a cylindrical axially extending tip. The tip is closed at its outer end by a pierceable plug that is trapped between an inner centrally apertured wall of the tip and an outer-end rim. The tubular guide sleeve, which has on its outer end a holder for a double-ended and pointed needle whose outer end is intended for insertion into a vein while its inner end projects so far into the guide sleeve that when the guide sleeve is fitted to the specimen tube it pokes through the plug, is axially shiftable and rotatable on the tip. The inner end of the needle projecting from the guide tube is contained in a bag-like tube (elastomeric needle-shield tube) of such length that the inner point of the needle does not initially reach to its closed end.
In order that the guide sleeve stays on the tip in spite of the spring pressure from the elastomeric needle-shield tube, the tip is provided with a laterally projecting bump for holding the double-ended needle that fits in an L-shaped slot in the guide sleeve. This holding bump projecting through the slot in the periphery forms a sort of bayonet latch that secures the guide sleeve to the double needle. Such a latch-ensures a solid connection of the fitted-together parts of the blood-drawing device, but increase its production cost. In addition the coupling and decoupling or latching of the guide sleeves requires that the holding bump first be aligned by turning of the specimen tube with the closing screw or plug cap to align with the slot, which requires some adept manipulation so that the parts can be properly aligned.
German 692 25 609 (US equivalent U.S. Pat. Nos. 5,154,285 and 5,277,311) describes a protective housing for a needle screwed into a needle holder. Here the protective housing is rotatable on the holder to which end the protective housing has a ring forming an inwardly open groove in which a ridge on a tip of the holder fits.